This invention relates to optical filters, in general, and to high performance optical wavelength filters, in particular.
It is desirable to provide high performance optical wavelength filtering for a variety of applications in the optical communications field. It would be highly desirable to provide a filter that has a broad optical tuning range, along with a fast tuning speed. Prior attempts to provide such a tunable filter have failed to provide a broad tuning range in combination with fast tuning speed. In prior tunable filters, the tuning speed is, at best, in the microsecond speed range, whereas a truly rapid tuning speed should be in the nanosecond speed range. In addition it is highly desirable that any such filter have an insertion loss of 2 dB or better. Until now, no existing filter technology meets these rigid requirements.
In accordance with the principles of the invention a switched optical wavelength selective reflector includes a bi-directional optical switch coupled to a plurality of wavelength selective reflectors. In one embodiment of the invention, the switch is a bi-directional optical switch having a first port and a plurality, N, of second ports. The optical switch is responsive to control signals for establishing an optical coupling between a first port and a selected one port of the plurality of second ports. Each of the second ports has coupled thereto one of a plurality of wavelength selective reflectors. Each of the wavelength selective reflectors is coupled to a corresponding one of the optical switch second ports. Each wavelength selective reflector is selected to reflect optical signals at a predetermined one optical wavelength selected from a plurality of predetermined optical wavelengths. Optical signals at a selected predetermined one optical wavelength received at the switch first port are reflected back to the first port by the switch selected one wavelength selective reflectors.
In accordance with one aspect of the invention the optical switch is formed on a first substrate of electro-optic material. In one embodiment of the invention, the substrate comprises LiNbO3.
In accordance with the principles of the invention, in one embodiment of the invention the optical switch comprises a 1xc3x97N switch.
Further in accordance with the invention, one embodiment of the invention includes a second substrate carrying the plurality of wavelength selective reflectors. In this embodiment, the second substrate comprises silicon and is bonded to the first substrate.
In accordance with another aspect of the invention each wavelength selective reflectors comprises a reflective filter. In the illustrative embodiment of the invention, each reflective filter comprises a fiber Bragg grating.
In accordance with another aspect of the invention, a bi-directional optical switch is formed on the same substrate as the plurality of wavelength selective reflectors. The optical switch is responsive to control signals for establishing an optical coupling between a first port and a selected one of the wavelength selective reflectors.